The present invention relates to an actuating device for a regulating flap in motor vehicles, such as a heater or ventilation flap, and, more particularly, to an actuating device which is configured to be movable about a pivot and, at least in a closed position thereof, rests against a stop which fixes the flap, comprising an actuating member, remote from the regulating flap, for actuation of the regulating flap, and a connecting rod operatively arranged between the regulating flap and the actuating member to convert an actuating stroke of the actuating member into a pivoting movement of the regulating flap.
A known actuating device is described, for example, in German Patent No. 935,597. To adapt the maximum actuating travel of the actuating member to the control travel required to close the regulating flap, starting from its position of maximum opening, adjusting elements are generally provided in the connecting rod.
An adjusting element of a known kind is described, for example, in DE 29 36 817 C2. It consists of two coaxial parts, screwed together, in the course of a force transmission member. One part is rested against an actuating bridge while the other part is connected via a sliding guide to a Bowden cable. By screwing one part further into the other part or screwing one part to a relatively great extent out of the other part, the length of the adjusting element can be altered and hence tolerances in the control travel of the actuating bridge compensated. Such adjusting elements require, however, additional assembly time and assembly costs. Moreover, these readjustment operations become extremely difficult and complicated if the force transmission member is concealed, as it frequently is, for example if the connecting rod is accommodated together with the regulating flap in the heater unit.
Tolerances in the control travel of the regulating flap arise only in the course of time and with relatively long use of the actuating device and hitherto regularly led to leaky regulating flaps with the necessity for readjustment in the workshop. Such leaks hitherto occurred regularly with air shut-off flaps, e.g. ventilation or heater flaps, which shut off the air passage opening in an airtight manner by means of a sealing lip. Ageing causes such sealing lips to settle and, as a result, the control travel for the regulating flap to ensure airtight closure of the regulating flap becomes gradually larger.
Windscreen wipers in motor vehicles are shown, for example, in DE 27 56 744 C2 in which resilient apparatus consisting of a first piston connected to one rod part, a guide cylinder connected to the other rod part and accommodating the piston in displaceable fashion, and a compression spring supported against the cylinder and the piston are provided in the wiper linkage. The compression spring presses the piston against a stop in the cylinder and is designed to be so strong that the resilient apparatus act as rigid connecting parts between the two rod parts during the operation of the wiper. The resilient connecting device in the known windscreen wipers serve the purpose, however, of enabling the wiper arms to be guided manually out of the well for the wiper arm with the wiper motor stationary, by pivoting in the wiping direction of the wiper arm, without damaging the wiper linkage. The manual pivoting forces exerted on the wiper arm are here taken up by the compression spring, which is compressed.
An object on which the present invention is based is to provide an actuating device for a regulating flap, in which no adjustment work is required and in which, on the contrary, tolerances occurring in the control travel of the regulating flap are compensated automatically.
The foregoing object has been achieved according to the present invention, in an actuating device for a regulating flap by providing a maximum actuating stroke of the actuating member is larger than a pivoting distance to be travelled by the regulating flap during transfer thereof from a position of maximum opening into the closed position against the stop to compensate for maximum travel tolerances. The connecting rod consists of two rod parts, one of which is coupled to the regulating flap and the other of which is coupled to the actuating member, and, the rod parts are operatively connected to one another to transmit an actuating force in a pulling and pushing direction, via an elastically compressible connecting member configured such that a required compressive force is greater than an actuating force to be transmitted over travel of the regulating flap to the closing position thereof.
In the actuating device according to the present invention, the greater size of the actuating stroke as compared with the control travel and the resilient connecting member between the rod parts of the two-part connecting rod ensure that the regulating flap is always reliably transferred into its closed position. A residual stroke of the actuating member which remains after this is taken up by compression of the elastic connecting member. As a result, even tolerances in the control travel of the regulating flap are automatically compensated.
With the actuating device according to the present invention, the elastic connecting member, which is compressed in the closed condition of the regulating flap, is, after travelling the increasing control travels, somewhat less compressed but still presses the sealing lip onto the rim of the air passage opening in a reliable manner.
The actuating device according to the present invention thus makes it possible to install the actuating device at the factory and to dispense completely with adjustment after assembly, and furthermore provides a long-term guarantee of reliable airtightness for regulating flaps used as air shut-off flaps.
In one currently preferred embodiment of the present invention, the elastically compressible connecting member is formed by a piston arranged on one rod part, a guide cylinder which is arranged on the other rod part and accommodates the piston in axially displaceable fashion, and a compression spring which is supported against the piston and against the base of the guide cylinder and brings the piston to rest against a stop on the guide cylinder. The prestressing force of the compression spring is configured to be greater than the actuating force required to close the regulating flap. As a result, the spring remains stiff over the entire control travel and is not compressed. The actuating stroke of the actuating member is thus transmitted to the regulating flap at a ratio of 1:1 over the entire control travel, and only after the regulating flap has been brought to rest against its stop is the remaining actuating stroke of the actuating member compensated by compression of the compression spring.